Light collection from diffractive displays

Abstract

A diffractive display system and a method of collecting first order light beams from a diffractive display of the system utilize holographic optical elements (HOEs) to deflect one of two first order diffracted light beams that emerge from each diffracting pixel of the diffractive display, so that the first order diffracted light beams can be separated from the zeroth order light beams. The utilization of the HOEs allows the system to be implemented in a compact optical configuration, without sacrificing any portion of the first order diffracted light. In a first embodiment, the system includes three HOEs that have static diffracting properties that are optimized for red, green and blue lights. For each set of light beams from a diffracting pixel of the diffractive display, the HOEs are holographically configured to deflect only one of the two first order diffracted light beams, such that the deflected first order light beam propagates in the same direction as the other non-deflected first order light beam. In a second embodiment, the system includes three HOEs that have reconfigurable diffracting properties that are also optimized for red, green and blue lights. In a third embodiment, the system further includes a holographic color filter that is comprised of three reconfigurable HOEs to sequentially illuminate the diffractive display with each of the tristimulus color lights.

What is claimed is: 
     
       1. A method of collecting useful diffracted light beams from a diffractive display comprising steps of: providing illumination light to said diffractive display;   diffracting said illumination light by said diffractive display to provide a zeroth order light beam and two first order light beams from a pixel of said diffractive display;   selectively deflecting one of said two first order light beams such that both of said two first order light beams from said pixel of said diffractive display are propagated in a substantially same direction; and   displaying said two first order light beams to present an image that is partially formed by said two first order light beams.   
     
     
       2. The method of claim 1 wherein said step of selectively deflecting a first one of said two first order light beams includes a step of holographically diffracting said first one by transmitting said first one through a holographic optical element. 
     
     
       3. The method of claim 2 wherein said step of holographically diffracting said first one of said two first order light beams is a step of holographically diffracting said first one by transmitting said first one through a color-sensitive Bragg-type holographic optical element. 
     
     
       4. The method of claim 3 wherein said step of transmitting said first one of said two first order light beams is a step of transmitting said first one through three color-sensitive Bragg-type holographic optical elements, each of said color-sensitive Bragg-type holographic optical elements being selective to a particular tristimulus color light. 
     
     
       5. The method of claim 2 wherein said step of holographically diffracting said first one of said two first order light beams is a step of holographically diffracting said first one by transmitting said first one through a reconfigurable holographic optical element that has been activated to a diffractive state, said holographic optical element having an optical state that is responsive to an applied electrical field. 
     
     
       6. The method of claim 5 wherein said step of holographically diffracting said first one of said two first order light beams is a step of holographically diffracting said first one by transmitting said first one through a color-sensitive Bragg-type reconfigurable holographic optical element that has been activated to said diffractive state, said color-sensitive Bragg-type reconfigurable holographic optical element having recorded interference fringes that are configured to be color selective with respect to diffraction. 
     
     
       7. The method of claim 1 wherein said step of providing said illumination light includes a step of filtering said illumination light with respect to wavelength by transmitting said illumination light through color-sensitive reconfigurable holographic optical elements, including sequentially activating one of said color-sensitive reconfigurable holographic optical elements to a diffractive state, said color-sensitive reconfigurable holographic optical elements having optical states that are responsive to an applied electrical field. 
     
     
       8. The method of claim 1 further comprising a step of optically removing said zeroth order light beam so that said zeroth order light beam is not displayed along with said two first order light beams. 
     
     
       9. The method of claim 1 wherein said step of providing said illumination light includes a step of generating high intensity white light to illuminate said diffractive display. 
     
     
       10. A diffractive display system comprising: light emitting means for providing illumination light;   image generating means optically coupled to said light emitting means to receive said illumination light for diffracting said illumination light such that, for each beam of said illumination light that is diffracted, a zeroth order light beam and two first order light beams are produced;   collecting means optically coupled to said image generating means for deflecting at least one of said two first order light beams such that both of said two first order light beams are propagated in a substantially same direction; and   displaying means optically coupled to said collecting means for visually presenting an image that is partially formed of said two first order light beams.   
     
     
       11. The diffractive display system of claim 10 wherein said collecting means includes a holographic optical element having recorded interference fringes to deflect a first one of said two first order light beams by diffraction such that both of said two first order light beams are propagated in said substantially same direction. 
     
     
       12. The diffractive display system of claim 11 wherein said holographic optical element of said collecting means is a color-sensitive Bragg-type holographic optical element. 
     
     
       13. The diffractive display system of claim 11 wherein said holographic optical element of said collecting means is a reconfigurable holographic optical element, said reconfigurable holographic optical element including a hologram that is configured to diffract said first one of said two first order light beams when said hologram is in a diffractive state, said diffractive state of said hologram being responsive to an applied electrical field. 
     
     
       14. The diffractive display system of claim 13 wherein said hologram of said reconfigurable holographic optical element includes recorded interference fringes to optically manipulate only a particular tristimulus color light when said hologram is in said diffractive state. 
     
     
       15. The diffractive display system of claim 13 wherein said reconfigurable holographic optical element includes a polymerizable monomer having dipentaerythritol hydroxypentacrylate that is combined with liquid crystal. 
     
     
       16. The diffractive display system of claim 11 further comprising a holographic color filter optically coupled to said light emitting means to receive said illumination light, said holographic color filter including a plurality of reconfigurable holographic optical elements, said reconfigurable holographic optical elements having optical properties that are responsive to an applied electrical field, each of said reconfigurable holographic optical elements being configured to transmit light of a particular color. 
     
     
       17. A method of separating first order diffracted light beams from zeroth order light beams that emerge from a diffractive display comprising steps of: transmitting illumination light from a light source to said diffractive display;   diffracting said illumination light by said diffractive display so that, for each diffracting pixel of said diffractive display, a zeroth order light beam and two first order light beams are generated; and   selectively deflecting a first one of said two first order light beams by holographically diffracting one of said two first order light beams using a holographic optical element such that both of said two first order light beams are propagated in a substantially same direction.   
     
     
       18. The method of claim 17 wherein said step of selectively deflecting said first one of said two first order light beams includes a step of transmitting said first one through a color-sensitive Bragg-type holographic optical element to effectuate said deflection. 
     
     
       19. The method of claim 17 wherein said step of selectively deflecting said first one of said two first order light beams includes a step of transmitting said first one through a reconfigurable holographic optical element that has been activated to a diffractive state, said reconfigurable holographic optical element having an optical state that is responsive to an applied electrical field. 
     
     
       20. The method of claim 19 wherein said step of transmitting said first one of said two first order light beams through said reconfigurable holographic optical element is a step of transmitting said first one through a color-sensitive Bragg-type reconfigurable holographic optical element that has been activated to said diffractive state, said color-sensitive Bragg-type reconfigurable holographic optical element having recorded interference fringes that are configured to be color selective with respect to diffraction. 
     
     
       21. The method of claim 17 further comprising a step of filtering said illumination light from said light source by transmitting said illumination light through color-sensitive reconfigurable holographic optical elements, including sequentially activating said color-sensitive reconfigurable holographic optical elements to a diffractive state from a passive state so that said diffractive display is sequentially illuminated by different tristimulus color lights, said color-sensitive reconfigurable holographic optical elements having optical states that are responsive to an applied electrical field.